Why I get different result when try Suzuki Abe border following method?

Question

In the paper by Suzuki Abe, I try the border following algorithm from their example:,

and here the algorithm:

My result from their algorithm is

It's different from the paper result, the result become -2 when in paper 2, when I process step 3.4 part a. Is it (i₃,j₃+1) mean coordinate column from current pixel+1?

Answer 1

Without seeing your implementation, it's hard to know for sure. But, my first guess is that, in your code, you're deciding to label a pixel as -LNBD only if is zero, instead of also confirming that this cell was examined your implementation of step (3.3). So, in your loop that implements (3.3), add a flag that flips to true when your counterclockwise search for a 1-pixel value hits , and then modify your implementation of step (3.4(a)) to also check this flag.

I encountered the same problem myself and didn't quite realize it until I read the proof of Lemma 2 on P 43.